The invention relates to a centrifuge with a vertical axis of rotation, with at least one skimmer that is accommodated in a skimming compartment in the centrifuge drum and that continuously diverts a liquid phase being clarified or separated in the drum, with a sealing disk that is rigidly connected to the skimmer above the skimming compartment, that extends into a blocking compartment rotating along with the drum and that can be filled with a blocking fluid, and wherein the skimmer is stationary and with the sealing disk are positioned at a distance from the rotating components of the drum.
Such a centrifuge is known from German Offenlegungsschrift 2 737 463. Centrifuges of this type are mostly employed to clarify or separate liquids that are sensitive to air and that must be kept away from bacteria. The sealing disk that is immersed in a blocking fluid above the skimming compartment is intended to prevent atmospheric air from entering the skimming compartment and hence the liquid being diverted from the compartment by the skimmer.
A fluid called a foreign fluid, because it is independent of the product being centrifuged, is usually employed as a blocking fluid in the blocking compartment because this compartment is in contact with the atmosphere and it is impossible to avoid at least some air getting into it.
Powerful eddies do, however, occur in the blocking compartment because of the stationary sealing disk being immersed in a rotating blocking fluid, causing the fluid to squirt into the skimming compartment, which is below the blocking compartment, and mix with the liquid being diverted from it. Thus, the effectiveness of clarifying or separation is powerfully affected by the foreign fluid.
Preventing the fluid from squirting out of an upper skimmer compartment into another skimming compartment below the first by positioning a catcher compartment below the first skimming compartment to return the overflow to the drum-feed space is known from German Auslegeschrift 3 006 200. A design of this type can only be employed, however, when the blocking fluid is the liquid phase being clarified or one of the liquid phases being separated, so that a certain amount of air getting in is acceptable.